The present invention relates to automatic control systems for motorized positioners in X-ray systems; and particularly to such control systems which detect and respond to collisions between the X-ray equipment and an object.
In relatively large X-ray systems, such as shown in U.S. Pat. No. 4,358,856, the X-ray source and film holder are mounted on a gantry which allows the components to be positioned at different angles with respect to the patient. For example, during angiographic procedures, X-ray exposures are taken of the patient at a number of angles from the frontal projection through a plurality of oblique projections to a lateral projection, and through a plurality of head to foot angles in concert with the frontal and oblique projections. In order to position the gantry at each of the angles at which an exposure is to be taken, a series of motors move the gantry components with respect to the patient. The electrical drive circuitry for each motor is controlled by a set of push buttons operated by the X-ray technician.
Because the X-ray equipment is moving about a relatively immobile patient, a safeguard mechanism must be provided in the event of a collision between the moving equipment and the patient. In the past, sensors were mounted on various components of the gantry which were likely to come into contact with the patient or the X-ray technician, during the operation of the equipment. In response to the sensors detecting a collision between the equipment and another object, the drive circuitry for the gantry motors was disabled until manually reset.
Although this safeguard technique prevented serious injury to the patient and to the X-ray technician, the individual or object with which the equipment collided might be wedged between different components of the X-ray system. Since the collision could occur due to a malfunction in the motor drive circuitry, the motor could not be used to move the equipment in the opposite direction to extricate the trapped individual. Furthermore, because of the motor gearing and the heavy weight of the gantry components, movement of the components by hand to free the individual was often extremely difficult.